Fortnightly Water Quality Report

Transcription

1 Fortnightly Water Quality Report Ichthys Nearshore Environmental Monitoring Program Weeks 66/67: 25 November 2013 to December 2013 Weeks 66/67: 25 November 2013 to 8 December 2013 Prepared for INPEX October 2014

2 Document Information Prepared for INPEX Project Name File Reference L384-AW-REP-10169_0_42_Water Quality Fortnightly Report Weeks 66_67.docm Job Reference Weeks 66/67: 25 November 2013 to 8 December 2013 Date October 2014 Contact Information Cardno (NSW/ACT) Pty Ltd Cardno (WA) Pty Ltd Cardno (NT) Pty Ltd Level 9, The Forum 11 Harvest Terrace Level 6, 93 Mitchell Street 203 Pacific Highway West Perth WA 6005 Darwin NT 0800 St Leonards NSW 2065 Telephone: Telephone: Telephone: Facsimile: Facsimile: Facsimile: International: International: International: Document Control Version Date Author Author Initials Reviewer Reviewer Initials A 17/12/2013 Chris Beadle CB Joanna Lamb JL 0 19/12/2013 Chris Beadle CB Joanna Lamb JL 1 14/10/2014 Chris Beadle CB Christopher Holloway CGH This document is produced by Cardno solely for the benefit and use by the client in accordance with the terms of the engagement for the performance of the Services. Cardno does not and shall not assume any responsibility or liability whatsoever to any third party arising out of any use or reliance by any third party on the content of this document. Prepared for INPEX Cardno Page ii

3 Table of Contents 1 Summary Reporting Period Trigger Exceedance Summary Summary of Dredge Operations 2 2 Wind, Rainfall and Tidal Conditions 3 3 Turbidity 5 Tables Table 1-1 Water Quality summary period 1 Table 1-2 Wet season trigger exceedance summary (25 November 2013 to 8 December 2013) 1 Table 1-3 Summary of East Arm Dredge Operations (data provided by INPEX) 2 Table 3-1 Summary notes on turbidity plots for the period 25 November 2013 to 8 December Figures Figure 2-1 Darwin Airport (data source Bureau of Meteorology) air temperature and atmospheric pressure, wind speed and direction and half hourly rainfall (daily totals presented numerically on top of plot) for the fortnight to 8 December Figure 2-2 Darwin predicted tide for the fortnight to 8 December, based on harmonic constituents for Darwin defined by the Australian Hydrographic Service ( 4 Figure 2-3 BoM AUSWAVE Model significant wave height the for output location 11 km north-north-east of Charles Point for the fortnight to 8 December Figure 3-1 Water Quality monitoring sites 6 Figure 3-2 Channel Island (reactive coral site) 7 Figure 3-3 Fannie Bay (reactive seagrass site) 8 Figure 3-4 Lee Point (reactive seagrass site) 9 Figure 3-5 Woods Inlet (reactive seagrass site) 10 Figure 3-6 Woods Inlet 2 (contingency reactive seagrass site) 11 Figure 3-7 Casuarina Beach (seagrass site) 12 Figure 3-8 Charles Point 2 (seagrass and coral site) 13 Figure 3-9 East Point (seagrass site) 14 Figure 3-10 Mandorah (coral site) 16 Figure 3-11 Northeast Wickham Point (coral site) 17 Figure 3-12 South Shell Island (coral site) 18 Figure 3-13 Upper East Arm 1 (harbour dredging site) 19 Figure 3-14 Weed Reef 1 (coral site) 20 Figure 3-15 Weed Reef 2 (coral site) 21 Prepared for INPEX Cardno Page iii

4 1 Summary This fortnightly report covers weeks 66 and 67 since the commencement of dredging operations for the Ichthys Project and the telemetered water quality data collected as part of the Water Quality and Subtidal Sedimentation Monitoring Program (25 November 2013 to 8 December 2013). The fortnightly report provides an assessment of the water quality trigger levels for the fortnight and has been based on this period to highlight the spring-neap tidal cycle. This report collates information from 13 different telemetered Water Quality monitoring sites selected to assess the turbidity associated with dredging and spoil disposal activities. Duplicate monitoring systems have been deployed at three reactive monitoring locations to provide backup data collection at these critical sites. 1.1 Reporting Period This Fortnightly Water Quality Report summarises dredging activities, metocean (wind, rainfall and tidal) conditions and water quality (turbidity) results for the period defined in Table 1-1. Table 1-1 Water Quality summary period Period Start Period End Monday, 25 November 2013 Sunday, 8 December Trigger Exceedance Summary Three Level 1 wet season seagrass triggers were exceeded during this reporting period at Lee Point (Table 1-2 and Figure 3-4). The reported trigger exceedances occurred during a neap tidal phase which experienced heavy rainfall, strong westerly winds, large swell and waves generated by Tropical Cyclone (TC) Alessia (see Section 2). TC Alessia formed on 20 November 2013 as a tropical low in the Indian Ocean south of Java, tracked eastwards and developed into a Category 1 cyclone on 22 November 2013, some 500 km west-south-west of Darwin. It made landfall near the Daly River Mouth on 24 November 2013 at 18:30 Australian Central Standard Time (CST) and weakened shortly thereafter. The severe metocean conditions produced strong littoral stirring resulting in significant regional increases in turbidity along the Western Australian and Northern Territory coastal strip, including Beagle Gulf. Catchment runoff from the Howard River into Shoal Bay is also likely to have contributed to the increased turbidity recorded at Lee Point, with intense turbidity plumes evident at the mouth of the river in satellite imagery. As such, these exceedances were not attributed to dredging, as detailed in the Exceedance Attributability and Implementation Report Lee Point 25 to 27 November 2013 [C075-AH-REP-10021]. No exceedances of the wet season trigger levels were recorded at Channel Island, Fannie Bay or Woods Inlet during this reporting period. Figures showing Darwin metocean information and all turbidity logging sites for the reporting period are included in Sections 2 and 3, respectively. Table 1-2 provides a summary of the trigger exceedances observed during the reporting period. Table 1-2 Wet season trigger exceedance summary (25 November 2013 to 8 December 2013) Intensity Frequency Duration Wet Season Coral Triggers >44 NTU >26 NTU > 6 days per 7-day rolling period >26 NTU over 7 consecutive days Channel Island None None None Wet Season Seagrass Triggers >63 NTU >52 NTU > 5 days per 7-day rolling period >52 NTU over 5 consecutive days Fannie Bay None None None Lee Point 25 to 27 November 2013 (n=3) None None Woods Inlet None None None Prepared for INPEX Cardno Page 1

5 1.3 Summary of Dredge Operations Dredging for the gas export pipeline (GEP) continued up until 28 November 2013, at which point the direct Trailer Suction Hopper Dredger (TSHD), Queen of the Netherlands, moved onto the East Arm dredging scope of works. During the reporting period TSHD operations of high spots and pipeline channel dredging occurred along the GEP route between Kilometre Post (KP) 864 and KP 877 (Mandorah and Middle Arm, respectively). East Arm dredging progress as of 8 December 2013 is approximately 48% complete. Table 1-3 provides a summary of East Arm dredge operations undertaken during the reporting period. Table 1-3 Activities Undertaken Summary of East Arm Dredge Operations (data provided by INPEX) The Cutter Suction Dredger (CSD) Athena recommenced dredging on 26 November 2013 in Separable Portion (SP) 4 (Turning Basin) before moving to SP5 (Walker Shoal) on 8 December 2013 after demobilising on 24 November 2013 in line with the Ports Cyclone Management Plan. During dredging, the CSD loaded TSHD Vox Maxima, Rotterdam (27 to 28 November 2013) and Queen of the Netherlands (28 November 2013 onwards). The direct TSHD Rotterdam operated in SP4 throughout the reporting period. Average Overflow Time* 14 minutes 34 seconds Volume Material Dredged (Reporting Period) ~460,800 m 3 *Average overflow time for both CSD and TSHD since the approval and implementation of average 15 minute overflow on 24 April Prepared for INPEX Cardno Page 2

6 2 Wind, Rainfall and Tidal Conditions Atmospheric conditions at Darwin Airport, sourced from the Bureau of Meteorology (BoM), are presented in Figure 2-1 and the predicted tides at the Port of Darwin are shown in Figure 2-2. The reporting period is characterised by strong westerly winds of up to 35 km/hr from 25 November 2013 to 30 December 2013, resulting from TC Alessia. From 1 December 2013 to 8 December 2013, recorded wind speeds were up to 25 km/hr with varying wind direction with the typical diurnal sea breeze cycle. Few notable rainfall events occurred during the reporting period, with 14.0 mm and 10.8 mm of rainfall recorded on 25 November 2013 and 2 December 2013, respectively. Cumulative rainfall for November 2013 was mm, which is substantially above the November monthly average of mm, indicating heavier than usual wet season rains for November The total number of rain days exceeding 1 mm for November 2013 was 17 days, compared to the November average of 10.1 days 1. Figure 2-1 Darwin Airport (data source Bureau of Meteorology) air temperature and atmospheric pressure, wind speed and direction and half hourly rainfall (daily totals presented numerically on top of plot) for the fortnight to 8 December BoM Climate Statistics for Australian Locations ( Prepared for INPEX Cardno Page 3

7 The maximum tidal range for the reporting period and 2013 was 7.5 m on 5 December 2013, with a minimum of 1.2 m on 27 November 2013 (Figure 2-2). Figure 2-3 shows significant wave height output from the BoM AUSWAVE model located approximately 11 km north-north-east of Charles Point (Latitude 12.3 º S, Longitude E). This figure shows the influence of TC Alessia on the Darwin wave climate. Modelled significant wave height peaked at 1.6 m on 25 November 2013, and remained above 0.5 m until 1 December 2013 before showing a gradual decrease towards the end of the reporting period to pre-tc levels. Figure 2-2 Darwin predicted tide for the fortnight to 8 December, based on harmonic constituents for Darwin defined by the Australian Hydrographic Service ( Figure 2-3 BoM AUSWAVE Model significant wave height the for output location 11 km north-northeast of Charles Point for the fortnight to 8 December 2013 Prepared for INPEX Cardno Page 4

8 3 Turbidity Fortnightly turbidity time series for the reporting period are shown in the figures below for all monitoring sites (Figure 3-1). Turbidity data is telemetered half hourly and daily averages calculated from the available readings (48 records per day) between 00:00 and 23:59 on each day. The data has been subjected to an automated three step QA/QC procedure including: > removal of negative values; > removal of flat line sections; and > removal of outliers by a de-spiking algorithm (Wong et al. 2012). In Figure 3-2 to Figure 3-15, the raw (half hourly) turbidity data are presented as a grey line and the daily average by the solid black line. The daily average turbidity is shown and the number of data points used in the calculation of the daily average is indicated at the top of the plot. Daily averages based on less than 48 points are generally due to the removal of points due to QA/QC procedures. The times of instrument servicing (should they fall within the fortnight) are highlighted by a green square ( Service ) symbol and missing data by red squares ( Suspect ) in Figure 3-2 to Figure 3-15 in accordance with the International Oceanographic Data and Information Exchange (IODE) procedure. Level 1 wet season trigger values for the reactive sites Channel Island, Fannie Bay, Lee Point and Woods Inlet are shown in Figure 3-2 to Figure 3-5. Table 3-1 provides summary notes on the information presented in the figures below. Table 3-1 Summary notes on turbidity plots for the period 25 November 2013 to 8 December 2013 Notes Daily average turbidity across the region (Figure 3-2 to Figure 3-15) shows marked differences between the Darwin Harbour Inner sites (Mandorah, Woods Inlet, Weed Reef, South Shell Island, Northeast Wickham Point and Upper East Arm) and Darwin Outer sites (Charles Point, Lee Point, Fannie Bay, East Point and Casuarina Beach). During the reporting period, the offshore zone (Darwin Outer) was affected by significant oceanic influences (waves and winds) resulting from the effects of TC Alessia which travelled eastward, making landfall approximately 150 km southwest of Darwin late on 24 November 2013 (see Section 2). Figure 2-3 indicates that offshore significant wave height (from the BoM AUSWAVE model output location 11 km northnorth-east of Charles Point) was high from 25 November 2013 to 2 December Significant rainfall at the end of the previous reporting period on 23 November 2013 and 24 November 2013 (Figure 2-1) and associated run-off from the catchments, particularly the large Shoal Bay catchment, most likely contributed additional suspended load to the coastal zone. Increasing sea state and littoral mixing in Darwin Outer coastal waters and rainfall appear to have contributed to the increase in turbidity within the coastal zone sites of Darwin Outer, most notably at the seagrass sites Lee Point, Casuarina Beach and Fannie Bay. Three Level 1 wet season seagrass triggers were exceeded during this reporting period at Lee Point (Section 1.2 and Figure 3-4). Turbidity was generally lower at the Darwin Harbour Inner sites (as expected during the neap tides), which were less impacted by oceanic conditions. Turbidity was generally greater during spring tides across the majority of the Darwin Harbour Inner sites. The maximum tidal range for the reporting period occurred on 5 December 2013 (7.5 m). On 14 November 2013, the Spoil Ground monitoring site was deployed at location 12 º S, 130 º E (see Figure 3-1), and immediately began recording data in the bottom logger. The site has not yet been facilitated with real time telemetry. Woods Inlet data quality deteriorated between 4 December 2013 and 8 December 2013 due to shorting of a cable connection. The Woods Inlet contingency site was transmitting during this period (see Figure 3-6). Mandorah data quality deteriorated between 5 December 2013 and 8 December 2013 due to a suspected wiper jam. Prepared for INPEX Cardno Page 5

9 Figure 3-1 Water Quality monitoring sites Prepared for INPEX Cardno Page 6

10 Figure 3-2 Channel Island (reactive coral site) Prepared for INPEX Cardno Page 7

11 Figure 3-3 Fannie Bay (reactive seagrass site) Prepared for INPEX Cardno Page 8

12 Figure 3-4 Lee Point (reactive seagrass site) Prepared for INPEX Cardno Page 9

13 Figure 3-5 Woods Inlet (reactive seagrass site) Prepared for INPEX Cardno Page 10

14 Figure 3-6 Woods Inlet 2 (contingency reactive seagrass site) Prepared for INPEX Cardno Page 11

15 Figure 3-7 Casuarina Beach (seagrass site) Prepared for INPEX Cardno Page 12

16 Figure 3-8 Charles Point 2 (seagrass and coral site) Prepared for INPEX Cardno Page 13

17 Figure 3-9 East Point (seagrass site) Prepared for INPEX Cardno Page 14

18 Prepared for INPEX Cardno Page 15

19 Figure 3-10 Mandorah (coral site) Prepared for INPEX Cardno Page 16

20 Figure 3-11 Northeast Wickham Point (coral site) Prepared for INPEX Cardno Page 17

21 Figure 3-12 South Shell Island (coral site) Prepared for INPEX Cardno Page 18

22 Figure 3-13 Upper East Arm 1 (harbour dredging site) Prepared for INPEX Cardno Page 19

23 Figure 3-14 Weed Reef 1 (coral site) Prepared for INPEX Cardno Page 20

24 Figure 3-15 Weed Reef 2 (coral site) Prepared for INPEX Cardno Page 21